Are We Living Inside a Simulation?

Why perception, memory, and certainty are less solid than they feel

For some time now, I have found myself increasingly curious about how the brain works. That curiosity did not begin in a classroom or a lab. It began with the knowledge that I was losing my central vision.

At first, my questions were practical. What was happening to my eyes? The photoreceptors were dying, which meant light was no longer being converted into the electrical signals my optic nerves needed to carry visual information to my brain.

Eventually, my curiosity moved upstream. What were those signals, exactly? Where did they go? And what did my brain do with them that gave rise to the experience of seeing at all?

Over the years since, that line of questioning has grown into a deeper fascination with neuroscience. In another life, I can imagine having pursued it formally. Today, it remains a curiosity, but not a casual one. I am not a subject matter expert by any means, but I have learned along the way that neuroscience sits at the very heart of who we are and how we experience the world. It offers an explanation for how raw sensation becomes meaning, memory, and our sense of a self moving through time and space.

Demis Hassabis, the founder of DeepMind, the research lab behind Google’s Gemini AI, is not only an AI researcher and executive, but a neuroscientist. His doctoral work focused on a deceptively simple question: what does the hippocampus do, a region of the human brain long thought to function primarily as a filing cabinet for memories?

Hassabis’s central claim was that the hippocampus is not merely a storage system for the past. It is something far more active. He argued that the hippocampus functions as a kind of simulation engine, one that allows the brain to construct scenes and mentally move through them.

He arrived at this idea by studying patients with damage to the hippocampus. These patients could still think. They could still reason. They could still speak fluently. What they had lost was the ability to place themselves inside a moment that was not immediately present.

From this, Hassabis proposed that memory, imagination, and planning are not separate mental functions. They are expressions of the same underlying capacity: our ability to simulate experience.

We remember the past by reconstructing it.

We imagine the future by assembling familiar elements into new configurations.

We make decisions by mentally rehearsing possible outcomes.

Simply put, we remember the past by simulating it. We imagine the future by simulating it. We make decisions by simulating possibilities.

If these ideas are correct, as mainstream neuroscience largely supports, then life as we experience it is not a direct encounter with reality itself, but a continuously updated internal model the brain constructs, through which we navigate the world.

That concept fascinates me. Hassabis is not claiming that reality itself is a simulation. He is arguing that the brain constructs a simulation of reality, and that our lived experience consists of navigating the world through that model, much the way a player navigates a video game environment.

That parallel is especially striking given Hassabis’s background. Before neuroscience and artificial intelligence, his early work was in game design, where the challenge is not to recreate reality, but to build a convincing, navigable model of it. That way of thinking later shaped how he approached the problem of building intelligent systems capable of learning, navigating, and acting within complex environments.

One place where this becomes especially relevant is our understanding of memory. We tend to think of memory as a faithful record, something stored and retrieved intact. In reality, memory as we experience it is a reconstruction, a simulation built from fragments, shaped by context, expectation, and emotion. That makes it useful, but also fallible.

As my vision has degraded, I have noticed this more often. Not in dramatic ways, but in small, unsettling moments.

Last summer, while walking along a trail, I suddenly froze. Stretched across the path in front of me was what looked like a snake. I startled, stopped short, and backed up, my body reacting before my mind had time to catch up. I stood there for a moment, trying to figure out how to get around it.

As I studied the scene more carefully, the snake slowly dissolved into a stick.

What struck me afterward was not that I had been mistaken. It was how complete the mistake had been. My brain had not offered a tentative guess. It had delivered a fully formed reality, complete with fear, urgency, and certainty. Only later did that simulation update itself.

After 9/11, researchers began studying what are known as flashbulb memories, the vivid recollections we form around emotionally charged events. People were asked to document their memories of that day immediately, then again months and years later. What emerged was not widespread forgetting, but confident distortion. The stories stayed vivid. The details drifted. Certainty remained even as accuracy eroded.

The hippocampus is not a vault for memory, but a stage on which memory is reconstructed. Each time we remember, we are not retrieving the past so much as rehearsing it, and each rehearsal subtly rewrites the script.

All of this raises a more practical question for me. Not about neuroscience or artificial intelligence, but about certainty.

If perception is a simulation, and memory a reconstruction, then much of what I experience with confidence is provisional. Useful, often reliable, but not fixed. The snake on the trail felt real until it wasn’t. My memory of events feels solid even as it quietly changes.

That realization suggests that what we call the self is not an entity at all, but an effect of ongoing mental processes.

It is a hard thing to get our heads around. It can sound as if I am saying there is no “me” at the center of everything. But what I mean is something quieter than that. The self, that felt sense of “me,” appears to be less a core, unchanging entity and more the result of a complex web of causes and conditions. Perception, memory, emotion, and narrative come together in a way that feels coherent and personal, even though nothing at the center remains fixed.

We tend to think of the self as something stable and enduring, the author behind our thoughts and the owner of our memories. But if memory is a rehearsal and perception a model, then the self begins to look less like an object and more like a process. Something assembled moment by moment, shaped by context, emotion, and attention.

Why this matters, at least to me, is that it softens certainty. If who I am is less a fixed core and more an unfolding experience, then my perspective is not the absolute truth of the world, only one way of seeing it. And if that is true for me, it is true for everyone else as well. 

Seen through this lens, our differences begin to make more sense. 

It becomes harder to assume that a belief different from my own is rooted in malice or ill intent. That does not mean harm does not exist. It does mean that understanding the causes and conditions that shaped a belief can open the door to compassion, even when disagreement persists. 

For me, the lesson in all of this is simple: we are far more alike than we typically feel comfortable admitting.

Accepting that changes how we relate to one another.

If something here felt familiar, I’d love to hear your thoughts, please Like it, or share it with someone who might appreciate it.